diff --git a/src/arch/riscv/prefix/libprefix.S b/src/arch/riscv/prefix/libprefix.S
index 583f27117..3fe01d7c8 100644
--- a/src/arch/riscv/prefix/libprefix.S
+++ b/src/arch/riscv/prefix/libprefix.S
@@ -204,6 +204,7 @@ early_uart_reg_base_64_done_\@:
 	.macro	print_char_uart_8250
 	early_uart_reg_base a7
 	sb	a0, EARLY_UART_8250_TX(a7)
+	fence
 early_uart_8250_wait_\@:
 	lbu	a1, EARLY_UART_8250_LSR(a7)
 	andi	a1, a1, EARLY_UART_8250_LSR_THRE
@@ -236,6 +237,7 @@ early_uart_8250_wait_\@:
 	.macro	print_char_uart_sifive
 	early_uart_reg_base a7
 	sw	a0, EARLY_UART_SIFIVE_TXFIFO(a7)
+	fence
 early_uart_sifive_wait_\@:
 	lw	a1, EARLY_UART_SIFIVE_TXFIFO(a7)
 	bltz	a1, early_uart_sifive_wait_\@